you should find the note you're singing then it's equivalent on tab notation, you can use a piano or guitar to help you find the note, then just find the rythm and all that and tab it, it's not easy though if you aren't used to tabbing

how would I tab the intro to bodies by drowning pool, considering it has no rhythm behind it?

There is rhythm. I think you meant there is no pitch. The solution to that is to use dead notes. Check the picture.

Note that since there is no pitch, I arbitrarily picked a line on the staff to place the dead notes. The middle line is suitable since it centers the eye in the middle of the staff, so don't go over-analyzing whether or not he is "whispering in B."

This tab has rhythm notated with the W, Q, and E symbols, etc., which stand for whole, quarter, and eighth respectively. Tabs in magazines like Guitar World have rhythms notated too, with stems and flags underneath the notes like in standard notation.